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Gonyaulacysta longicornis
Riding et al., 2022 elevated the subspecies Gonyaulacysta jurassica subsp. longicornis
Deflandre 1938 to species rank. However in doing so, an illigitimate junior homonym of Gonyaulacysta longicornis (Downie 1956) Sarjeant 1969 was created. To remedy this, Riding et al., 2025 proposed a new name Gonyaulacysta nasuta as substitute for G. longicornis Deflandre 1938.
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Original description (Deflandre, 1938) (translated from French):
Gonyaulax jurassica Deflandre var. longicornis n. var.
Plate VI, Fig. 6.
This variety differs from the type only in its general shape, the tabulation remaining the same as far as I could ascertain. The epitheca is elongated conical and extends into a long horn, nearly twice as long as in the type. This elongation is mainly due to the development of the apical plates, but the pre-equatorial plates also appear to contribute to the more slender appearance of the epitheca. The sutured ribs, in the few individuals observed, and especially in the one drawn as the type, are less developed and less spiny, especially compared to the very rounded specimens of G. jurassica.
The type of the variety longicornis measures 88 μm long, 54 μm wide, and the horn alone reaches nearly 30 μm.
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Emended description Riding et al., 2022:
Emended diagnosis: A large, usually elongate, epicavate species of Gonyaulacysta with a very prominent apical horn (c. 30% of the entire cyst length) formed of periphragm. The tabulation is reflected by denticulate sutural crests and ridges, and the sulcus is longitudinal, L-type.
Emended description: A large species of Gonyaulacysta which is normally markedly elongate. The cyst is epicavate, and has a distinctly angular, three-sided hypocyst. The epipericoel is large, and the precingular and postcingular plate boundaries may exhibit suturocavation. This species has a very long, slender, distally truncate apical horn composed only of periphragm. The apical horn length comprises about 30% of the overall length of the entire cyst. The endocyst normally exhibits a small, rounded apical protuberance. The tabulation is complete, and is reflected by sutural crests and ridges that are distally denticulate. The cingulum and the sutures surrounding the 1′′′′ plate may have evident gonal spines (up to c. 5 μm). The sulcus is L-type and longitudinal. An opisthopyle is either absent, or not observable because the endophragm and periphragm are in contact in the antapical region. The periphragm is generally smooth, but occasionally may bear low-relief ornamentation such as scabrae. The endophragm is thicker than the periphragm and consistently smooth. The periarchaeopyle is large, and may extend substantially above the top of the endocyst.
Holotype: Specimen AM60 of Deflandre (1938, pl. 6, 6). Sample from the lower Oxfordian Marnes de Villers Formation (Quenstedtoceras mariae ammonite zone), Villers surMer, Calvados, northern France. Curated in the Institut de Paléontologie, Musée Nationale d'Historie Naturelle, Paris, France.
Comments: Gonyaulacysta longicornis was originally described from the lowermost Oxfordian of northern France by Deflandre (1938) as a variety of Gonyaulax jurassica in order to accommodate specimens with long apical horns. This taxon was transferred to Gonyaulacysta as a variety of Gonyaulacysta jurassica by Downie and Sarjeant (1965, p. 115), then elevated to subspecies level by Lentin and Williams (1973, p. 62). Sarjeant (1982, p. 31) re-assigned this taxon as a variety of Gonyaulacysta jurassica subspecies adecta. He deemed Gonyaulacysta jurassica var. brevis (Johnson and Hills, 1973) to be a taxonomic junior synonym of longicornis. Riding (2005b) and Riding et al. (2010) used the terms ‘elongate morphotype’ and ‘large morphotype’ respectively as suffixes following Gonyaulacysta jurassica subsp. adecta var. longicornis simply to emphasise the unusually elongate ambitus of this taxon. In our view, this taxon fully justifies species status. It has an extremely distinctive morphology and a restricted stratigraphical range (see below). Our present emendation emphasises that Gonyaulacysts longicornis is large, epicavate and has a very long, slender, distally blunt apical horn.
Comparison: The species most similar to Gonyaulacysta longicornis are Gonyaulacysta ceratophora and Gonyaulacysta dualis. However, these species are bicavate and typically exhibit low sutural ornamentation. Tabulation in Gonyaulacysta ceratophora is absent except in the polar areas and the sutures in Gonyaulacysta dualis are typically distally smooth. In overall morphology, Gonyaulacysta longicornis also resembles Gonyaulacysta adecta, but the latter species is significantly smaller, has a relatively short apical horn, and is less elongate (Fig. 2B).
Dimensions: Based on 30 specimens measured herein, the dimensions of Gonyaulacysta longicornis are as follows: length of pericyst, 73 (91) 118; length of apical horn, 20 (25) 33; length of epipericyst, 40 (64) 78; length of hypopericyst, 13 (22) 29; length of endocyst, 47 (57) 73; width at cingulum, 44 (57) 84 (Supplementary material Appendix 3, table 10). This is consistent with the measurements of the type material by Deflandre (1938, p. 171): length of pericyst, 88; length of apical horn, 30; width at cingulum, 54.
Geographical and stratigraphical distribution: Gonyaulacysta longicornis has only been reported from Laurasia. It has been recorded from England, Greenland, Norway, Russia, Scotland and Svalbard. Records with ammonite control indicate that this species is a reliable marker for the late Callovian (Peltoceras athleta ammonite zone) to the middle Oxfordian (Cardioceras tenuiserratum ammonite zone) interval. It is usually sporadic and relatively rare in the late Callovian, but is consistently common in the early and middle Oxfordian (Riding and Thomas, 1997, figs. 2, 3; Riding et al., 1999, fig. 25; Riding, 2005b, figs. 3, 4; Ilyina et al., 2005, figs. 3, 7). The records of Gonyaulacysta longicornis in the latest Bathonian and early Callovian of eastern England by Riding (1987, fig. 4) are misidentifications of Gonyaulacysta adecta. Smelror and Below (1992, fig. 3) recorded Gonyaulacysta longicornis from the upper Callovian and lower Oxfordian of the Barents Sea. This species has also been observed in the upper Callovian and Oxfordian of Arctic Russia, Greenland, Arctic Norway and Svalbard by, for example, Bjærke (1977), Thusu (1978), Lund and Pedersen (1985), Smelror (1986, 1988a, 1988b) and Århus et al. (1989). In view of the many reports of Gonyaulacysta longicornis from the high northerly latitudes, this species was probably a relatively coldwater form (Riding and Michoux, 2013).
Deflandre 1938 to species rank. However in doing so, an illigitimate junior homonym of Gonyaulacysta longicornis (Downie 1956) Sarjeant 1969 was created. To remedy this, Riding et al., 2025 proposed a new name Gonyaulacysta nasuta as substitute for G. longicornis Deflandre 1938.
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Original description (Deflandre, 1938) (translated from French):
Gonyaulax jurassica Deflandre var. longicornis n. var.
Plate VI, Fig. 6.
This variety differs from the type only in its general shape, the tabulation remaining the same as far as I could ascertain. The epitheca is elongated conical and extends into a long horn, nearly twice as long as in the type. This elongation is mainly due to the development of the apical plates, but the pre-equatorial plates also appear to contribute to the more slender appearance of the epitheca. The sutured ribs, in the few individuals observed, and especially in the one drawn as the type, are less developed and less spiny, especially compared to the very rounded specimens of G. jurassica.
The type of the variety longicornis measures 88 μm long, 54 μm wide, and the horn alone reaches nearly 30 μm.
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Emended description Riding et al., 2022:
Emended diagnosis: A large, usually elongate, epicavate species of Gonyaulacysta with a very prominent apical horn (c. 30% of the entire cyst length) formed of periphragm. The tabulation is reflected by denticulate sutural crests and ridges, and the sulcus is longitudinal, L-type.
Emended description: A large species of Gonyaulacysta which is normally markedly elongate. The cyst is epicavate, and has a distinctly angular, three-sided hypocyst. The epipericoel is large, and the precingular and postcingular plate boundaries may exhibit suturocavation. This species has a very long, slender, distally truncate apical horn composed only of periphragm. The apical horn length comprises about 30% of the overall length of the entire cyst. The endocyst normally exhibits a small, rounded apical protuberance. The tabulation is complete, and is reflected by sutural crests and ridges that are distally denticulate. The cingulum and the sutures surrounding the 1′′′′ plate may have evident gonal spines (up to c. 5 μm). The sulcus is L-type and longitudinal. An opisthopyle is either absent, or not observable because the endophragm and periphragm are in contact in the antapical region. The periphragm is generally smooth, but occasionally may bear low-relief ornamentation such as scabrae. The endophragm is thicker than the periphragm and consistently smooth. The periarchaeopyle is large, and may extend substantially above the top of the endocyst.
Holotype: Specimen AM60 of Deflandre (1938, pl. 6, 6). Sample from the lower Oxfordian Marnes de Villers Formation (Quenstedtoceras mariae ammonite zone), Villers surMer, Calvados, northern France. Curated in the Institut de Paléontologie, Musée Nationale d'Historie Naturelle, Paris, France.
Comments: Gonyaulacysta longicornis was originally described from the lowermost Oxfordian of northern France by Deflandre (1938) as a variety of Gonyaulax jurassica in order to accommodate specimens with long apical horns. This taxon was transferred to Gonyaulacysta as a variety of Gonyaulacysta jurassica by Downie and Sarjeant (1965, p. 115), then elevated to subspecies level by Lentin and Williams (1973, p. 62). Sarjeant (1982, p. 31) re-assigned this taxon as a variety of Gonyaulacysta jurassica subspecies adecta. He deemed Gonyaulacysta jurassica var. brevis (Johnson and Hills, 1973) to be a taxonomic junior synonym of longicornis. Riding (2005b) and Riding et al. (2010) used the terms ‘elongate morphotype’ and ‘large morphotype’ respectively as suffixes following Gonyaulacysta jurassica subsp. adecta var. longicornis simply to emphasise the unusually elongate ambitus of this taxon. In our view, this taxon fully justifies species status. It has an extremely distinctive morphology and a restricted stratigraphical range (see below). Our present emendation emphasises that Gonyaulacysts longicornis is large, epicavate and has a very long, slender, distally blunt apical horn.
Comparison: The species most similar to Gonyaulacysta longicornis are Gonyaulacysta ceratophora and Gonyaulacysta dualis. However, these species are bicavate and typically exhibit low sutural ornamentation. Tabulation in Gonyaulacysta ceratophora is absent except in the polar areas and the sutures in Gonyaulacysta dualis are typically distally smooth. In overall morphology, Gonyaulacysta longicornis also resembles Gonyaulacysta adecta, but the latter species is significantly smaller, has a relatively short apical horn, and is less elongate (Fig. 2B).
Dimensions: Based on 30 specimens measured herein, the dimensions of Gonyaulacysta longicornis are as follows: length of pericyst, 73 (91) 118; length of apical horn, 20 (25) 33; length of epipericyst, 40 (64) 78; length of hypopericyst, 13 (22) 29; length of endocyst, 47 (57) 73; width at cingulum, 44 (57) 84 (Supplementary material Appendix 3, table 10). This is consistent with the measurements of the type material by Deflandre (1938, p. 171): length of pericyst, 88; length of apical horn, 30; width at cingulum, 54.
Geographical and stratigraphical distribution: Gonyaulacysta longicornis has only been reported from Laurasia. It has been recorded from England, Greenland, Norway, Russia, Scotland and Svalbard. Records with ammonite control indicate that this species is a reliable marker for the late Callovian (Peltoceras athleta ammonite zone) to the middle Oxfordian (Cardioceras tenuiserratum ammonite zone) interval. It is usually sporadic and relatively rare in the late Callovian, but is consistently common in the early and middle Oxfordian (Riding and Thomas, 1997, figs. 2, 3; Riding et al., 1999, fig. 25; Riding, 2005b, figs. 3, 4; Ilyina et al., 2005, figs. 3, 7). The records of Gonyaulacysta longicornis in the latest Bathonian and early Callovian of eastern England by Riding (1987, fig. 4) are misidentifications of Gonyaulacysta adecta. Smelror and Below (1992, fig. 3) recorded Gonyaulacysta longicornis from the upper Callovian and lower Oxfordian of the Barents Sea. This species has also been observed in the upper Callovian and Oxfordian of Arctic Russia, Greenland, Arctic Norway and Svalbard by, for example, Bjærke (1977), Thusu (1978), Lund and Pedersen (1985), Smelror (1986, 1988a, 1988b) and Århus et al. (1989). In view of the many reports of Gonyaulacysta longicornis from the high northerly latitudes, this species was probably a relatively coldwater form (Riding and Michoux, 2013).